Blumenbach's formative drive theory. Title page and frontispiece of the 1781 book 'Uber den Bildungstrieb und das Zeugungsgeschafte' (On the Formative Drive of the Generation Process) by German physician Johann Blumenbach (1752-1840). The frontispiece shows examples of reproduction and growth: a hen laying an egg, a woman breast-feeding, a grafted fruit tree, an infant with a missing limb, a child with a missing hand, and a man sowing seed. At right, in the circular illustration, a salamander's tail is being cut off for a medicinal preparation. The German text includes the author details and the publisher Johann Christian Dieterich of Gottingen.